Systems, apparatus and methods of treating and disinfecting water are of obvious and often critical importance. Access to safe water for drinking, cooking, bathing, and washing is obviously a basic human need. To ensure such safe water, drinking water and water used for industrial, agricultural, household or recreational use is often and advantageously purified. Thus, for example, spas, jetted (hot) tubs, whirlpools, wave pools baths, ponds, water tanks, swimming pools and the like are often treated with active compounds to maintain the water therein in a purified or sanitized condition. These active compounds, such as chlorine and ozone, have been used to sanitize the relatively large volumes, for example, hundreds or thousands of gallons, of water in such spas, tubs, etc. As used herein, the terms “spa” and “jetted tub” refer to systems which hold or contain a body of liquid aqueous medium, hereinafter referred to as water, which is often heated, in a reservoir which is smaller than a swimming pool, but is sufficiently large so that an adult human being can be completely submerged or immersed in the water contained in the reservoir. As used herein, Jacuzzis, baths, ponds, whirlpools, wave pools and swimming pools can be small or large, such that an adult human being, or several adult human beings can be completely submerged or immersed in the water contained in the reservoir.
Spas, jetted tubs and pools are often used by submerging all or a major portion of one's body in the water in the reservoir for recreation and/or relaxation. Additional, separate purifying or sanitizing components are also included in these waters to control bacteria, viruses, algae, etc., which are known to contaminate such waters. Very low concentrations of these active materials are used in order to avoid harming sensitive parts of the body—since such spas, tubs, pools etc. are sized so that the entire body can be immersed in the water and to minimize costs, because of the relatively large volume of water to be treated. For example, the normal (that is the typical, non-acute contamination) concentration of ozone used to purify or sanitize the water in a spa, tub or pool is often in the range of about 0.005 to about 0.05 parts per million (ppm) based on weight of ozone per volume of water (w/v).
Similarly, laundered fabrics are, by definition, soiled or dirty, and may also contain bacteria, virus particles, algae and fungi. Water used to launder clothing and other such fabrics is generally and advantageously treated before and/or after use, for example, to avoid recontamination of the fabrics or to lower the possibility of raising the infective load of such organisms in the environment.
Also, agricultural products, such as (without limitation) leafy produce (including lettuce, cabbage, parsley and the like), legumes (such as beans and peas), tomatoes, tubers (such as potatoes, beets, radishes and the like) all receive agricultural water, and various fertilizers. As a result of the use of certain sources of water or fertilizers there have been reports of bacterial and viral contamination of such foodstuffs. Disinfection of water for watering through the use of disinfecting agents (e.g., ozone and/or chlorine) can help lower the likelihood of food contamination. Ozone is an ideal agent for such disinfection, since it decomposes quickly into molecular diatomic oxygen, and leaves no aftertaste or residue on the food.
For similar reasons, treatment of, for example, drinking water with ozone provides water disinfection and purification without significantly affecting the taste of the water prior, for example to bottling.
Ozone (O3) has conventionally been used in industrial as well as household applications for purifying and deodorizing air, other gasses and the like. Ozone is an allotrope of oxygen, and is a relatively high-energy molecule (and quite unstable) when compared to molecular diatomic oxygen O2, and decomposes to molecular oxygen according to the equation 2O3→3 O2 in about 0.5 hours under normal conditions at standard temperature and pressure (STP). Ozone is a powerful oxidizing agent and this ability contributes to its utility as a disinfectant.
Under natural conditions ozone is most plentiful in the atmosphere, in a region of the stratosphere called the ozone layer, located between about 6 and about 31 miles above the surface. Stratospheric ozone is produced from the interaction of ultraviolet rays with diatomic oxygen in the following reactions:O2+photon->2O  (1)O+O2->O3  (2)
For most personal and industrial uses, ozone is generated using an ozone generator. The easiest and most cost effective manner of generating ozone is using the “coronal discharge method”, in which high voltage is generated across a dielectric component located between two electrodes. A gap through which air or oxygen may be passed is also located between at least two electrodes. The spark generated across the dielectric component causes the formation of free radicals of oxygen, and subsequently the formation of ozone in a two-step reaction similar and corresponding to the formation of ozone from diatomic oxygen shown above.
Ozone generators are therefore generally known in the art. However, the generation of ozone creates certain problems particular to the process. Therefore, for example, high concentrations of ozone can be chronically corrosive to materials, such as (without exception) metals, alloys, and rubber. Further corrosion may be caused when air rather than pure oxygen is used as the source of diatomic molecular oxygen and nitrogen containing salts and acids can be formed. All of this material can thereby shorten the useful life of an ozone generator and other related equipment, conduits, hoses, housings, contacts, fittings, pipes, wires and the like located in close proximity to the ozone generator.
In response to this problem, Harter et al., U.S. Pat. No. 4,049,707 constructed an ozone generator comprising a first electrode, a composite dielectric structure containing at least one layer of a first dielectric material including overlapping, flat, plate like particles of an inert dielectric material located directly against a second electrode. The first electrode and composite dielectrics structure are separated so as to define the gap. The gap comprises a chamber in which air or oxygen may be permitted to flow, and in which ozone may be generated from the air or oxygen. Additionally, the surfaces of the first electrode and of the dielectric structure exposed to the gap are coated with a material that protects the interior surfaces of the gap. Harter discusses an ozone generation having at least two different dielectrics, one comprised of plate-like particles and in which the ozonation chamber is coated with titanium dioxide.
As indicated above, in addition to the corrosive effect of ozone itself, when ozone is generated using air, which contains about 70% nitrogen, nitric acid is formed particularly when the air is moist or humid. This nitric acid also shortens the life of the entire ozone generator system. Similarly, under certain conditions ammonium nitrate may form on the dielectric, electrode(s) or other parts of the ozone generator.
In Lee et al., U.S. Pat. No. 6,730,277, an ozone generator is disclosed which is reported to be capable of producing ozone with much less consumption of electric power than previous models. The ozone generator features a pulse generator for generating high voltage pulses and a discharge chamber for inducing electrical discharge in response to the high voltage pulses. Electrical discharge takes place between electrode plate and a grounded chamber wall; a sheet of oxide dielectric covers the chamber wall to prevent corrosion of the chamber wall.
In Borgstrom et al., U.S. Pat. No. 6,726,885, an apparatus and method for generating ozone is disclosed in which a generally symmetrical device comprises a first electrode arranged along a longitudinal axis. The electrode is proximal to a first dielectric component on a top side, and a second dielectric component on a bottom side. A top coronal discharge chamber and a bottom coronal discharge chamber are arranged between the first dielectric and a top second electrode and the second dielectric and a bottom second electrode.
Sali et al., U.S. Pat. No. 5,354,541, discloses an ozone generator comprising a helical spring anode within a sealed glass dielectric tube. And a metal tube cathode spaced across an annular gap from the glass tube.
Mechtersheimer, U.S. Pat. No. 4,960,570, discloses an ozone generator in the form of a pair of outer electrodes and a tube or layer of tubes having a diameter corresponding to the space between outer electrodes, and having in each case an inner electrode. This configuration is stated to have the advantage of dispersing heat rather quickly.
Arlemark, WO97/01507, is said to have the advantage of being produced in a high frequency alternating current with high voltage over a dielectric. Oxygen is introduced between two plates of aluminum oxide and a current is applied to an electrode net in the device.
Yomomi, U.S. Pat. No. 5,435,978, is directed to a plate like ozone generator comprising a plurality of discharging cells stacked one over the other under pressure in a pressure vessel.
Morita et al., U.S. Pat. No. 6,039,816, discloses a compact ozone generator comprising three layers of a dielectric, in which the first layer has a filamentous electrode attached to the top surface, the middle layer has an induction electrode on the surface thereof and the third layer has a heating coil located on the top surface thereof. The heating coil is for evaporating ammonium nitrate that may adhere to the discharge unit when humid air is used as the oxygen supply. The three layers are sandwiched together.
Ozone mixed with oxygen or air can be produced by passing oxygen gas (O2), for example, from a gas cylinder or an oxygen-containing gas, such as atmospheric air or air from an air blower, by the high voltage “coronal” discharge method. Large-sized ozone generators for industrial use generally employ pure oxygen or dry air as a starting material, whereas small-sized ozone generators for household or personal use employ untreated air as a starting material. Such air-using ozone generators have the disadvantage, as discussed above, that when the ozone generator is discharged continuously, corrosive or contaminating nitrogenous compounds such as ammonium nitrate or nitric acid may form or be deposited on the electrodes or other portions of the ozone generator as a result of their reaction with nitrogen in air, resulting in corrosion or otherwise interfering with the function of the device. More particularly, because untreated air often has a humidity percentage higher than that of artificially-produced dry air, large amounts of nitrogen oxides can be produced when ozone is generated by discharge.
Accordingly, when so corroded or contaminated, the density of the electric field generated by the ozone generator can be reduced. Also, salts such as ammonium nitrate covering the filamentary discharge electrode may tend to absorb water present in the air and become electrically conductive, thus increasing the apparent area of one or more electrode.
That is, in a conventional ozone generator, because salts and corrosive materials such as nitric acid may corrode or cover the electrode(s) of the ozone generator, the density of the electric field generated by the filamentary discharge electrode is reduced. The capacitance of the dielectric increases, resulting in reduced ozone generation.
Conventionally, therefore, the conventional ozone generator is periodically disassembled, and adhering ammonium nitrate is wiped off from the filamentary discharge electrode using water or a solvent. That is, a conventional ozone generator must be maintained through manual labor. After cleaning, the ozone generator resumes discharging to thereby generate ozone.
Typically, also, ozone is generated on site for use in, for example, applications including the purifying spa/tub/pool waters. Although ozone generators used for such service can, in addition to those employing coronal discharge, include apparatus containing a sealed ultraviolet (UV) light lamp. Such conventional ozone generators are generally effective, in that they will produce ozone for oxygen-containing gasses. However, these generators do have certain drawbacks that other ozone generators disclosed elsewhere herein do not have. For example, the UV light lamp is relatively bulky, can burn out (often requiring system disassembly and lamp replacement) and systems containing such lamps are relatively inefficient in producing the desired amounts of ozone.
Therefore, it would be advantageous to provide new ozone generators that address these problems, and systems for purifying waters used for example (and without limitation), in agriculture, food and drinking water applications, for household applications such as laundry (e.g., washing machine) and dishwashing applications, spas, jetted tubs and pools comprising such ozone generators.
Each and every patent, patent publication and other publication cited in this patent application is hereby incorporated by reference herein individually and in its entirety.